Hello, I accidentally solved a memory leak just by enabling "with-rtsopts=-T". I knew where the issues was, in one servant client web call. It was showing even when the call result (a Bool) wasn't used. While the leak was "active", I had: ghc-options:   -threaded   -rtsopts   -with-rtsopts=-N And now that it doesn't show anymore, I have: ghc-options:   -threaded   -rtsopts   -with-rtsopts=-N   -with-rtsopts=-T I can reproduce the leak just by commenting out "-with-rtsopts=-T" and force rebuilding. Can anyone explain what is happening? Best regards, vlatkoB